In recent years the amount of information available in digital form has grown significantly. Digital data, which is easily reproduced and distributed, but retains superior quality, has been extremely beneficial to information and media content providers. The advantages for content providers, however, are not absolute. The same factors that make digital data attractive as a distribution format, i.e. high quality, easy reproduction and easy distribution, apply equally to pirates who make and distribute unlicensed copies of the data. Furthermore, with access to distribution mediums like the Internet millions of unlicensed, pirated, copies can be created effortlessly. This type of unlicensed copying is already widespread in the music industry with users of peer-to-peer file sharing services, like Gnutella, and costs the music industry millions in potential revenues.
Copy protection techniques exist in the prior art to address these issues. For example, the content can be tied to the user's device by encrypting the content with a key unique to the device. This approach, however, severely limits what valid licensed users can do with their content. Consumers expect to be able to have some freedom in the way they use their content. They expect to be able to transfer the content to other devices they use; and, they expect to be able to make back-up copies to protect their content in the event of a hardware failure. Purchasers of music, for example, expect to be able to listen to the music they purchase at home, on their car stereo, and on portable audio devices. Accordingly, overly restrictive systems that prevent these types of uses are unlikely to be accepted in the marketplace.